The functioning of disk brakes is affected negatively by contamination, which can lead to changes in friction, uneven wear and also corrosion on disks and linings. It is known to equip disk brakes with a protection plate so as to avoid contamination spattering directly onto the brake disk. The contamination may consist of, for instance, water contaminated with dust, salt and/or mud. The protection plate can be configured so that it covers the brake disk effectively but, when the brake disk is completely covered, cooling is also impaired. A common compromise between covering and cooling the brake disk is for the protection plate to cover the inside and the periphery of the brake disk. The outer side of the brake disk is partly protected by the wheel rim. The protection plate covers that part of the brake disk which is uncovered; that is to say, the part which is not covered by the brake caliper and brake lining.
Brakes on vehicles such as heavy-duty trucks, exemplarily configured as disk brakes, are sometimes subjected to very high power dissipation. In this connection, problems can arise if brake disks do not receive sufficient cooling. It has been found that the power dissipation is usually quite low at low speed. In many cases, low speed is due to a poor road standard, for example in the case of transporting lumber on forest roads, the road environment usually being very dirty as well. Construction vehicles also are driven at low speed when the environment is dirty, for example in the case of road construction. In this connection, it is desirable for the protection against dirt to have maximum effectiveness when the vehicle is driven at low speed.
On good roads, the speed is normally considerably higher, with an increased requirement for high braking effect. In this connection, it is desirable for the cooling to have maximum effectiveness. These varying requirements can be satisfied by a mechanical device which can adjust a damper or the like which adapts the admission of cooling air to the brake according to the current need. It is necessary, however, that such devices cannot be put out of operation, which in turn could lead to impaired braking effect; that is to say, the overall safety of the vehicle being put at risk.
Such a device adapted for motorcycles is known, for example, from JP05060158, which discloses a protection plate for a disk brake. In this example, a damper plate is displaceable along the outer edge of the protection plate being maneuverable by means of a piston cylinder for exposing a number of hole openings. This known solution is complicated and sensitive to contamination, for which reason it is not a realistic possibility for application to heavy-duty trucks, which are expected to cope with service intervals of roughly 50,000 km. Such a configuration, however, would be a prohibitively expensive solution for a truck which has at least four brake disks. Moreover, the solution is intended primarily for a brake disk which is covered on both sides, which is the case on motorcycles.